CA2085371C

CA2085371C - Combined syringe and needle shield

Info

Publication number: CA2085371C
Application number: CA002085371A
Authority: CA
Inventors: Daniel Andreas Talonn; Alan Bernard Ranford
Original assignee: Sherwood Medical Co
Current assignee: Covidien AG
Priority date: 1991-04-15
Filing date: 1991-04-15
Publication date: 1998-11-17
Anticipated expiration: 2011-04-15
Also published as: CA2085371A1; WO1992018183A1

Abstract

The invention provides a medication containing syringe (150) which includes first (166) and second (210) tubular members; a plunger rod assembly (154); a distal needle assembly (176) and a collar member (186). The first tubular member (166) includes distal and proximal ends and a slidable member (171) received therein which is adapted to retain a prefilled quantity of medication distally thereof. The plunger rod assembly includes a reciprocally mounted plunger rod (154) adapted to operatively contact the slidable member (171) through the proximal end of the first tubular member (166). The nee dle assembly (176) includes distal and proximal ends and a needle hub (174) thereon wherein the needle hub (174) is mounted adja cent the distal end of said first tubular member (166) and the needle assembly (176) also includes a distal needle point ( 179) on the distal end thereof and the proximal end of the needle assembly is adapted to be in fluid communication with the medi cation retained distally of the slidable member (171). The collar means (186) is operatively connected to the distal end of the first tubular member (166) and the second tubular member (210) is positioned about the first tubular member (166) and the collar m eans (186). The second tubular member (210) includes distal and proximal ends and is designed to slidably contact the collar means (1 86) longitudinally movable over the first tubular member (166) and the collar means (186) between a retracted position whe rein the distal needle point (179) is exposed and an extended position wherein the distal needle point (179) is protected. The second tubular member (210) further includes a tapered section (216) on the distal end thereof and the outer diameter of the di stal end of the tapered section (216) is substantially smaller than the outer diameter of the proximal end of the second tubular member (210) and when the second tubular member (210) is in the retracted position, the distal end of the second tubular member (210) is adjacent to the needle hub (174) and the distal end of the first tubular member (166).

Description

WO 92/18183 PCrtUS91/02579 ~ g'~j',7 1 :.
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cr~RJ~n SYRINGE ~D NEEDLE 5~T~T-n ! .
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T~is appli~ation i~ dire~d to an inv~ntion which is a d~elop~n~ 3~ our ~ pean ~a1:~nt applicatlPn No. 350 5 18~.
This inv~n~ion relat~s ~o Sl~yT:~g2S~ and, ~or example to a conv~antion~l syris~ge o~ the t~pe 2~dapted ko r~ eive a tiv.~ c~o~ artric~ re!~ n b~at h~v~ n~ ~ novel ext~n~ le needle nhield pri~arlly ror ~~~ L~JcJ!~ 0 - 10 ~JLiaV~}Lirlg or mia~i~izing ~ ci'~tall ne~dlq~ ~lck~.

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~o~ ~yringes used today ~or ~dical, l~boratory or d~ntal ~uL~o~e~ ar~ ~old as ~po~h~e it~s ~n~ e~l to be used only once. Di~posal of $u~h ~yr~nge~ has po~d a 15 saf~ty hazard ~or the in~iv~u~ s ~oho u~ ~e 6yringes as i~. well as ~or those who d ~ ~pO~13 of ~, ~ith the o~set of AIDS, the ~ollca~ for infection du~ to ~cci ~l~ntal ale~dle stick~ fro2~ used E;yrirlges; ha~ creaE;efl ~nd a ~r.r of :~' di*feren~ d@vice~ hav~ been ~IILi~ ttl ~inimiz~ ~he 20 possibility of spre~; nq inff~ctiou~ e~C e due to ~:
a::c:idents o~ this type. '~, One approach to this probl~ iie to provide an extendable needle shield which, after the ~yringe has be~n used, can be pushed to an extended position where it covers ' 25 the needle, ~aking it difficult for an individual to i accidentally contact the needl~. A co~mon feature of such ~ construction~ i.5 that when the needle shield is pushed to .~ its ext~n~ed position, it is locked so that it cannot be retracted (thu~ exposing the needle) except by application 30 of ex~raordinaxy force.
A number o~ such constructions have ~een proposed to satis~y the general requirement that the needle be permanently covered after the syringe has been used. Some '~': . ' .~., .

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of these constructions involve complex locking mechanisms and, in others, locXing occurs a,utomatically when the shield is ~ully extended. These known devices satisfy many ~: o~ the functional requir~ments of a needle shield but require, in most cases, ~odification o~ the ~tandard syringe construction. This is highly un~esirable ~or many manu~acturars because of the siz~le invest~n~ they may have already made in their existing ~olding equipment for producing the ~yringes.
Constructions have also been propo~d which include an opening or slo in th~ side o~ the shield. ~his is : undesirable because the needle can extend through the op~nin~ if the needl~ or the needle shield is deflec~ed when the needle shield is in the extended po~ition. Other .. 15 ~ osed device~ include open ended needle shields which :~ may not block access to the n~edle point by mall fingers. -' Tho~e devices which lock in response to axial ~.~vl- ont of the needle shield to the extended position, (i.e., without any ro~ation) hav~ cer~ain inherent drawbacks ~hat xesult primarily ~ro~ the re~uir~ent that 8u~8~ntial ~orces be exerted to lock the ~hield in it~ extended position. In the first place, the likelihood of : : unintentional and irreversible locking is greater with such devices than with those devices whirh require rotation to lock. Also, in certain con~tructions, it may be di~ficult to veri~y that the ~eedle shield i5 locked upon extension without attempting to retract the shield, which increases the possibility of unintended exposure of the nePdle.
In addition to the desi~n requirements described above, the des:ign of this type of dental syringe must allow for the insert:ion of a medication cartridge through the ,' proximal end O:e the den~al ~yringe. Additionally, the outer diameter of the distal end of thP needl~ shield . should be minimized so that the dentist is abl~ to bett2r observe the needle of the dental syringe during the use ., 1:1 ',: ': . ' ' ::: . ~'' "; . ' :. ., . .' ~-0 9~,~lXlX . I'C~/~S9~/()'57') : 2~37~

thereoI and so that the distal end of the needle ~hield does not interfere with the pl~c~m~t or u~e of other instruments which may simultaneously be present in the ; patient ' s mouth.
Accordingly, it is an obj ect of this invention to provide a protective needle ~hi~ld of the type described above which can be add~d at r~ l expen~e to ::onventional ~- hypodermic or dental syringes~
Another objest of the present invent1 on is to provide 10 a relatively in~Yp~n~ive protective shi~ld which satisfies the functional requirements of a r~ dle ~hi~ld and which .~ includes none o~ the ~1. a~.~acks mentioned abov~ ~
Another obj ect of the pre~ent lnve~tion is to provide . .
an extenc~hle needle shield for a dental syringe which 15 perfor~s all of the 7-~c~ s~ry functions o~ such ~ shield and which is par1:icularly well suited to an automated ~:~
process oî manufacture. .
~-~ A further object of the present invention i to .~i provide an exten~hle needle shield ~or a ~t2ndard - 20 hypodermic or dental eyringe which iis i~proved both from s: the points of view of ~unctio~al utility and cost of manufacture.
A still furth~r object of the pr~senk inv~ntion is to : provide an inexpensi~e method of assem~ling a protective ~: 25 needle shield and dental syringe.

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.: DISCLOSURE OF THE INVENTION
In accordance with the invention, a needle shield is mounted coaxially on a syringe barrel. ~he needle shield includes one or more elongated keys on its inner surface.
. 30 A collar is provided on the dii~tal end Q~ the ~arrel i: adjacent ko the needle or needle hub. The collar may be a 'I, .
separate part or it may be integrally ~ormed with the . .
barrel and includes on its outer surface at least one . .
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~, lockiny slot. The key slides in a path outside OI the locking 610t and can be rotated into the look; ng slot wh~n the needle shi~ld is ~xt~ e~ th the c:ollar and shield can be ~ol~ d ~rom plastic :materials ~;o that the cost of 5 the shield is relatively low.
In the pre~erred embodimenk, th~ ne~dle ~h~eld includes a plurality of elongated locking key~ and the collar inc:ludes a plurality of locki n~ slots . :~ach loc7cing slot i6 de~ined by opposing walls, at le2~t one o~ which 10 includes a ramp over which the keys can rid~2 when the shield is in its extQnded position and ~l~hse~uenkly ro~at~d to an ext~r~fle~q and locked pos~tion. As ~he 3c~ys are rotated into the loç~i ng slots, rearwart31 move~ent of the needle shield lto its retracted po~ition i~ preventad by a - 15 s~lrfac:e on the c:ollar at the back of eas::h lo~ki~g ~lot.
In accordance with on~ feature of the prs~ent invention, protrusions on the collar and the ~oxward portions o~ the keys are shaped such that during assembly, the keys are directed into keyways ~ormed between the locking slots as ~he collar is ~oved relative to the needle . shield. Thus, the construction i5 well suited to an auto~ated process in which the collar and need~e shield are secured to the standar~ hypod~rmic or dental ~yringe by ~ machine.
.~ 25 A further feature of the present invention i5 the .;:. provision of a needle shield hav.ing a reduced diameter distal end to allow for the attachment of a needle protecting needle sheath thereon.
Other features of the pres~nt invention are set forth :~ 30 hereina~ter in the detailed description of the preferred embodiments.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of an embodiment of the pr~sent invention shown mounted on a conventiona1 dental syringe with the needle shield in the extended position;
Figure 2 is a 5ide ~leval_ion view, partially in cross-section taken along lines 11~D1} as 5hown in Figure 1 and shown with th~ medication cartridge in the dental syringe and with the needle shield in the retracted position; .
Figure 3 is a fragmentary ~ide cross-s~ctional view also taken along lines 11~ s shown in Figure 1 and : shown with the needle shield in the extended position;
Figure 4 is an enlarged scal~, fragmentary side sectional view taken along lines 13 -13 as shown in Figure 2 and showing details o~ the collar and n~edle shield ; 15 thereof;
.~ Figure 5 is a fragmentary ~ectional view taken along lines 14--14 in Pigure 2 and showing a portion of the needle shield in the extP~d position prior to rotation of the needle shield;
~ 20 Figure 6 is a fragmentary ~ectional view taken along .~ lines 14--14 in Figure 2 and showing a porkion of the needle ~hield in the extended and locked position after .- rotation; ~nd ,......... Figure 7 is an enlarged scale, perspective view of the 25 col~ar shown in Figure 2, :.
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:~ DETATT~n DESCRIPTION OF THE PREFERRED EMBODIMENT
. In the pre~erred embodiment, the invention is intended to be used in conjunction with a standard hypodermic syringe: however, a protective needle shield in accordance 30 with the inVention may be modi~ied for use with any ; medical, laboratory or dental device having a needle, such " ~7~Pr~

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~ 3~ 6 as a blood collection tube ho.lder or dental syringe with a double ended needle (as descr:ibed hereinafter) without departing from the contemplat~d scope of the present invention. Accordingly, as used herein, the term "syringe"
is intended to include any meclical or scientific device including a needle wherein it is desired to protect a user from accidental needle stic~s.
In d~scribing the invention, th~ "di~tal end" of a : part refers to the end of the part close~t to the needle point. The "pro~;~al endt' o~ a part re~ers ~o the end ~urthest from the needle point.
An embodiment of the present invention is illustrated in Figures 1 through 7 with the collar and needle shield -~ adapted for use on a conventional dental syring~ o f the :' 15 type adapt~d to receive a medication cartridge removably ~ounted therein. Th~ dental syringe of the present ~mbodiment is generally designated as dental syringe 150.
~' As illustrated in Figures 1 and 2, the dental syringe ,j~ 150 of ~he present e~bodiment includes an elongate and tubular cartridge holder a~embly lÇ6 adapted to receive a : conven~ional medication cartridge 167 therei~
conventional injector ~s~hly 1~ is mounted on the pro~i -1 end of the cartridge holder as~embly 166. The : distal end o~ the cartrid~e holder asse~bly 166 includes a '. 25 double ended needle assembly 176 mounted ther~in and a tubular collar ~ss~ ly 186 mounted thereon. The collar : assembly 186 slidably contactC an elongate and tubular needle shield ~sel hly 210 which is longitudinally movable over the cartridge holder assembly 166 and the collar as~embly 186. A conventional needle sheath assembly 220 is removably mounted on the di~tal end of the needle shield : assembly 210.
As illustrated in Figure 2, the cartridge holder assembly 166 of the present embodiment includes an elongate and tubular p~.oximal barrel section 1~8, a tapered barrel .
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section 170 fixedly mounted on the distal end thereof and '' an integral distal barrel section 172 on the distal end of the tapered barrel section 170. The proximal end of the proximal barrel section 168 includes a pair of radially S exte~1ng ret~ntion flanges ~, the function of which are described hereinafter. The interior surface of the proximal barxel sPction 168 has a gen~rally uniform internal diameter which is adapted to receive a conventional medication cartridge 167 therein.
As illu~trated in Figure 2, the medication cartridge ; 167 referred to herein is a co~er~ially available medication cartridge having an i~j~ctable medication therein, one example o~ which is a 1.8 ml cartridge whirh contains a 2% liAoç~ine HCl injection with epinephrine in a concentration of 1.100,000 manufactured by Astra: ;
Corporation of Worchester, Nassachusetts, U~S~Ao The medication cartridge 167 includes an eiongate glass cylindQr 1~ with a rubber pi5ton or plunger m~mber 171 -.
movably mounted in the pro~t~l end of the cyli~der 165~ ; -The distal end of the ~edication cartridge 167 includes a - ~etal cap 173 ~ixedly muunted on a reduced portion of the ~, ~ylinder 165. The ~etal cap 173 includes a central orifice (not shown) positioned over a needle pierc~ahle diaphragm - 17~
As furthex illustrated in Fisure 2, the tapered karrel section 170 at khe distal end of the ear~ridge holder .~ assembly 166, decreases in external diametar from the ~' distal end of the proximal barrel sec~ion ~68 to a smaller diameter and integrally conneated, cylindrically-shaped distal barrel section 172. The external surface of the distal barrel section 172 preferably includss four equally spaced ribs 184 thereon (Figure 3). The distal end of the ~ ribs 184 extend from the distal end of the distal barrel :: section 172 so that the outer diameter of the .- ~
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The barrel section 172 surrounds the needl~ hub 174 of the integral double ended nee~le assembly 176 as illl~strated in Figure 2~ The n~edle assembly 176 further : includes an elongate and hollow distal needle section 178 which extends beyond the distal end o~ the cartridge holder assembly 166 to a sharpened dis~al needle point 179 and an integral and elongat~ hollow proximal ne~dle sectian which extends in~o and within the distal e~d o~ th~
cartridg~ holder ~c~ hly 166 to a ~harpened proximal : needle point ~1 located proximally o~ the taper~d barrel sec~ion 1~0. ~ cylin~rical cartridg~ posi~ioning hub 182 ~; is locat~d on the proximal sid~ o~ the needl~ hub 174 and extends pzo~ ~lly ~rom the needle hub 174 to a location generally adjac~nt to the midpoint o~ the tapered barrel section 170. The positioning h~b 182 encircles and . supports the majority of the pro~ l needle section 180 and is adapted to contact the distal end o~ the medication car~ridge 167 when the medication cartridge 1~7 is inserted i~to the cartridge holder a~se~bly 166 as described hereina~ter.
As illustrated in Figures 3 and 7, the tubular collar as~embly 186 of the pres~nt ~mbo~ t pre~rably includes six equally ~pa~ed and integrally ~ormed tria~gularly-:~- sh~ped protrusions 1~ which extend radially from the circumPerential ~ur~ace of the collar assembly 186. The apex of each o~ the triangularly-shaped protrusions 188 is .~ positioned along the pro~ ] side o~ the collar assembly 186 to assist in the assembly o~ the present e~bo~ t as described hereinafter. Each of the protrusions 188 also inc}ud~ a~yled ~urfac~s 18~a and ~ , side ~urfaces 19Z, ~: and a di~tal su:rface 1~ which extend pe~pendic~larly from -~ the sur~ace of the collar assembly 186. A recessed slot ; 35 ~ extends distally from the ap~x of ~ T ~ E T
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2-~537~

each of the triangularly shape!d protrusions l~ ~o a sloped distal surfacP 194A, the funct.ion of which is described hereinafter. The distal surface 196 o~ each protrusion 188 forms a generally circum~erential surface along the distal side 4f the protrusion 1~8 approximately midway along the : external sur~ace of the collar as~embly 186. Th~ side sur~aces 192 of each adjacent pair of protrusions lB~ form ~ keyways 190 therebetween, the function of which is ; described hereinafter. A radially extending and spherical detent ~Q~ is positioned in the keyway~ 190 between each ~. pair of protrusions 188 such that the distal edge of each '; spherical detent 208 is located lightly distal to khe distal surface 196 o~ each ~Lut~uslon 1~8 and the proximal edge of each ~pherical detent 208 is located slightly proximal to the side surfaces 192 of each protru$ion 188.
:~ A~ illustrated in Figures 5 and 6, a pair of parallel walls, ~Q~ and 204, are positioned radially along the lengthwise dimen~ion of the collar a~embly 186 adjacent to the distal surface 196 of each ~ sion 188. ThQ walls, ~ 20 202 and 204, form a rectan~ularly shaped locXing 510t 206 -~i therebetween, the ~unction of which is described ., hereinafter. The wall~, 202 and 204, preferably include a ramp shaped wall surface on thP external ~ide thereof and a perpendi~ulax wall surface on th~ internal side thereo~.
;-25 The surface o~ the lo~ki n~ Clot 206 is slightly elevated relakiv~ to the level of the keyways 190, i.e~, the collar diameter at the loc~ing slots 206 is slightly greater than .the collar diameter at the keyways 190. This slight increase in collar diameter at the locking slots 206 removes some o~ the slack or wobble which may occur between the needle ehield asse~bly 210 (described hereinafter) and th~ collar as;se~bly 186 to decrease the likelihood that the needle shielcl assembly 210 will wobble or move relativ~ to the cartridg~ holder assembly 166 whe~ the needle shield ... .

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W0 92/lX183 1?Cr/l.,-S~ 579 asse~bly 210 is moved to a locked and extended position (Figure 3) described hereinafter.
- As illustrated in Figure 4, the internal surface of :: the collar assembly 186 includes a wedge shaped internal 5 tooth ~ her ~1~ adjac~nt to the proximal end of the collar assembly 186 which is adapted to engage the outer surface of the distal barrel section :172 and retain the collar assembly 186 on the distal barrel section 1~2 of the cartridge holder asse~bly 166 during assembly of the 10 pre~ent ~ hodiment as described hereina~ter. The collar ~: assembly 1~6 of the present embo~i ~nt is molded of a riyid plastic ma~erial such as a polycarbonate resi~ 80 that the collar as~bly 186 c~es ~ ~llght de~ormation o~ the ribs 184 and distal barrel section 172 as the collar assembly 186 placed on the distal barrel ~ection 112 of the cartridqe holder asse~bly 16S. Alternately, raised yieldable ribs ~not ghown) ~ay be ~o~med on the distal ~; barrel section 172 or gaps may be formed in the tooth ?r 212 o~ the collar to function in the sa~e manner as ~ 20 described above with respect ~o the preferred ~mbo~ nt.
'i Additionally, other m2a~s of interlo~ the collar 186 to , ~ the distal barrel ~ection 172 ~uch as ultrasonic welding or 3 adhesives ~re contemplated and may be used without departing from the scope of th~ present .in~ention.
With reference to Figures 1 and 2 of the drawings and as heretofore described, the cartridge holder assembly 166 of the pres~nt ~ 3~;ment includes a conventional injector ~ ~-q~ hly 152 mounted on the prox; ~l end ther~o~. The .t injector ass~mhly inclu~es a bore ~53 therethrough for .. 30 slidably receiving an elongate plun~er rod 154 therein.
The plunger rod 154 is provided with a çonventional ~-. enlarged and circular ~inger ring 1~ at the proximal end thereo~ and a triangularly-shaped and sharpened barb member extending ~rom the distal end thereof. The injector 35 a~sembly 152 ~uxther includes a ~enerally cyl.indrical body ., .
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section 151 having a proximally positioned enlarged oval-shaped finger flange 160 which is adapted to be grasped by the fingers of the user. A cylindrical locking ring 162 is slidably positioned on the body section 151 of the injector assembly 152 distal to the finger flange 160. The body section 151 also includes a generally cylindrically-shaped and resilient, body member 164 which extends distally from the finger flange 160. The body member 164 includes an integral and furstoconically-shaped distal portion 161 having a retaining lip or rim 164A thereon. A pair of longitudinally extending slots or channels 165 are provided on opposite lateral sides of the body member 164. Each channel 165 includes a triangularly-shaped recess 163 adjacent to the distal end thereof which is adapted to receive one of the retention flanges 169 from the cartridge holder assembly 166 therein, as will be discussed more fully hereinafter.
As illustrated in Figures 3 and 4, the needle shield assembly 210 of the present embodiment preferably includes an elongate and tubular proximal shield section 214 having three equally spaced and rectangularly-shaped elongate keys 198 integrally formed along the interior surface thereof and a tapered shield section 216 which decreases in external diameter from the distal end of the proximal shield section 214 to an integral distal shield section 218. The keys 198 preferably extend lengthwise between the distal and proximal ends of the proximal shield section 214 and include triangularly-shaped distal ends and flat-proximal ends, the function of which are described hereinafter. An end rim 222 is formed along the inner surface of the proximal end of the proximal shield section 214 and is adapted to extend radially inwardly therefrom.
Three equally spaced and inwardly extending oblong-shaped detents 200 are formed along the internal surface of the distal end of the needle shield assembly 210. These WO 9'/18~X~ PC~/l,S')I/0257') :L2 detents 200 are preferably spaced approximately thirty degrees from an adjacent key :L98 and include sloped distal surfaces, the function of which are described hereinafter.
The distal shield section 218 o~ the needle shield asse hly 210 is a cylindrically shaped tubular me~ber having a centrally located neeldle aperture ~11 therein, as . illustrated in Figures 2 and 3. The needle aperture 211 o~
the distal shield section 218 is sized to allow the distal needle section 178 and the needle hub 174 o~ the needle - 10 assembly 176 to pass therethrough~ ~he tapered shield section 216 and th~ red~?~e~ diam~ter distal shield section 218 allow the dentist to observe the antire distal needle sectio~ 178 of the ~eedle ~R3i--' ly 176 during a dental ~ pro~ure and does not inter~ere wi~h a~y other ins ~L I ~nt~
.. ~ 15 which ~ay be si~ultaneously present in the pa~-ient's mouth.
~ Additionally, ~he use of the tap~r~d ~hield ~ction 216 and '~ . the smaller sized needle aperture 211 reduces the likelihood that a child or person with s~all ~i~gers may ac~ ntally contact the distal needle point 179 when the naedle shield asse~bly 210 is in the extended position as :.~ described her~inafter.
As brie~ly described above, the needle ~heath assembly 220 is adapted to be L~ ' vably atta~hed to the di~tal shield 6ect~0n 218 o~ the needle shield assembly 210. As .~ 25 illu~trated in Figures 1 and 2, the needle ~heath ~5l hly . 220 includes an elongate and tubular body section 221 which ~, is ~dapt~d to prot~ct th~ distal n~edla section 178 and distal needle point 179 of the needle asse~bly 176 prior to ., use of the pre~ent e~bodiment. The proximal end of th~
needle sheath as~embly 220 include~ an enlarg~d rim member ' 2~ The proximal end o~ the needle sheath assembly is .~ adapted to b~ attached to the distal s~ction 218 of the needle ~hield a~semhly 210 by ~rictional conta~t, adhesives or heat staking thersbetween.
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, ~ WO9~/18i83 PCT/I,S'JI/OZ57'1 2 a ~ i 3 7 3 - Assembly o~ the dental syringe 150 is r~latively simple and may be automated. Initially, the collar as~embly 186 is positioned within th~ pr~Y~ shield section 214 of th~ needle shi~ld assembly 210 by inserting 5 the collar assembly 186 through th~ distal end of the prox~ hield sectio~ 214 so that the triangularly-shaped distal ends of the keys 198 are position between the ~ triangularly-sh~pe~ pro~rusiorls 188 and in th~ appropriate ; keyways 190 on the collar ~qs~mhly 185. The tap~red shield section 216 and integral di~tal shield section 218 are then placed on th~ distal ~nd o~ the proxi~al ~hield section 214 ; so that the t~pered shi~ld section 216 is ret~ine~ on the di~tal end of the proYi ~l shield section 214~ This may be ~çc ~lish~d by ultra~onic welding, adhesiv~s or interlo~k;ng mechan~cal engage~ent o~ a grooved sidewall with a co~pl~2ntary dls~ally ext~n~ proj~ction 228 located at the distal en~ of the proximal shield section 214 as illustrated in Figu~ 2. ~he needle shield ~SSpmhly ~i 21U and collar assembly 186 are then telescoped over the ; 20 distal ~nd o~ the cartridga holder ~ hly 166 so hat the ~ tooth ~mb~r 212 o~ the collar a~embly 186 is forced over .. ~ the distal ~arrel ~ection 172 by the ne~dle s~i~ld assembly : 210 until the proxi~al end of the collax a~se~bly 186 is ~r.y~y~d on the distal barr~l section 172 in a predetermined location.
In the present ~mbodiment, the rim member 223 of the needle sheath assembly 220 i~ the~ attached to the distal 1.
~' shield section 218 of the needle shield assembly 210.
' Alternately, if the needle ~ mhly 176 is separate from .' 30 the distal barrel ~ection 172, the needle hub 174 of the needle a~embly 176 is attach~d to the dis~al barrel '~ section 172, as descrihed above, and then the needle sheath a~~embly 220 i5 attached to the distal shield section 21%.
~, It is also contemplated that the other.assemhly ~thods described above with respect to the preferred embodiment :, , .

WO 92/1~18'~ PCr/~S~J1/0257 1~

are readily adaptable for the assembly of the dental syringe 150 of thP present e~odiment.
The dental syringe 150 of the present embodiment raay be used in a oorlventional Dlanner to perform various dental 5 procedures. Initially, the user may insert a ~edication cartridge l67 into the proximal end o~ the cartridge holder assembly 166 . The plunger rod 154 of th~ in~ ector assembly lS2 is then moved proYiln~.lly to a retracted po~ition and the inje~::tor assembly 152 is at:tached to th2 cartridge .~ 10 holder assembly 166 by in~erting the r~tention ~langes 169 ~-~ o~ the cartridge holdex assembly 166 into th~ recesses 163 located in çh~nne] s 165 of the in; ector assembly l52 . The user ~ay then lock the injector assembly lS~ an the proximal end of the car~ridge holder as~;embly l66 by moving . ~ 15 the locking ring 162 distally along the body m~mber 164 ~o ;; compres the ~rus~oconically-~haped distal portion 161 of the b~dy menber 164 to retain the retention flanges 16g of the cartridge holder ;~;r hly 166 within the recPsfies 163 .. in the ~~h~n,ol~s 165 of the body h~r 164. The user may 20 thell ~rasp the ~inger ring 156 on the injector ~g~- '-ly 152 .' and ~ov~ th~ plunger rod 154 distally until th~ barb member 158 pierce~ and i5 seat~d in th~ plunger aleDIber 171 on prc~ l end of the medication cartridge 167 and the proYi -1 needle point 181 pierces the diaphragm 175 through 25 the orific~ in 'che ~etal cap 173 on the distal end of the m6~dication cartxidge 167.
As illustrated in Figure 2, the ~edication cartridge - 167 is loaded in the cartridge holder a~se~ly 166 and the needle shield ~;Pmhly 210 is in the retract~d position.
In the ret:racted position, the needl~ shielcl assembly 210 is positioned about th~ cartridge holder a~;sembly 1~6 ~o that the pro.f- ~1 end of the pro~ shield sectiorl 214 is adjacent to the lip 164A o~ the body member 164 on the ;
injector assembly 152; the needle aperture 211 on of the ': 35 di tal shield section 218 is adjacent to the needle hub 174 ; ~ 5~;~V, ~1 i E~ ~ .~; ~EVI

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: 15 . , of the needle assembly 176 and the needle sheath as5embly 220 encloses the distal needle seckion 178 and distal needle point 179 of the needle assembly 176. In the retracted position, the triangularly-shaped distal ends of the keys 198 are positioned in the k~yways 190 bekween ~he side surfaces 192 of the protl~sions 188 and in contact with the proximal edge of the spherical detents 208 on the collar assembly 186. Additionally, the detents 200 on the needle ~hield 210 are ali~ned within the slots 194 on the protrusions lB8 so that the pro~i -1 surfac~ o~ the detents , 200 will contact the slop~d distal ~ur~ace 194A of the : slots 194 to releasably retain the needle shield asse~bly :~ 210 in kh~ retracted position.
In order to a~mj~ister an inj~ction, the needle sheath assembly 220 is initi~lly r~u~ed from the di~tal shield section 218 to expos~ the distal n~edle point 179 of the needle ~s~mhly 176. The user may then admi ni ster the l injection in a conventional ~~ner by inserting the distal - needle point 1~9 into the injection site while grasping the ~i~ 20 finger flange 160 a~d moving the ~inger ring 155 on the -: plunger rod 154 di~tally ~ith respect to the finger flange 160. The di~tal movement oS the plunger rod 154 causes the ' barb ~ her 158 to move the plunger member 171 distally in .'~; the cylinder 165 of th~ medication cartridg~ 167 and dispense th~ medication through the distal needle point 179 on the needle ~sPmhly 176 and into the injection site~
once the contents o~ the dental syringe 150 have been injected into the patient, the needle shield assembly 2~0 is pushed distally to the extended position as shown in Figures 1 and 3. As the ne~dle shield asse~bly 210 is ~. moved to the extended position, the keys 198 will slide .: longit~l~inAl].y in the keyways 190 over the sph~rical .~ detents 208 on the collar assa~bly 186 and the angled distal sur~aces on the de-tents 200 on the needle shield assembly 210 will slide over the angled detenting surfaces e~ S ~
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WO 92/1X183 PCr/~,S~)1/02S79 ~ r 194A on slots 194 to release the needle shield assembly 210 from the retracted position. As the needle shield assembly 210 reaches the ext~nde~ position, the spherical de~ents : 20a on the collar 186 will signal the user that the needle shield assembly 210 has reachl~d the fully extended position by releasing from the ~lat proximal ends o~ the keys 198, once the keys 198 pass beyond the spherical detents 20~.
Additionally, as illustrated in Figure 3, when the needle shield ~cs~ ~ly 210 reaches the extended position, the end 10 rim 272 on the proxi~al end o~ the needle shield assembly ~: 210 will contact the proximal end o~ the collar assembly ': 186 to prevent further distal ve~e~t of the needle shield ~SE ~ly 210 along the cartrid~e holder ~ss~ ~ly 156 and the collar ~c- ~ly 186.
A~ generally illustrated in Figures 3 and 5, when the ne~dle !3hield ~ fi~ hly 210 is in khe extexlded position, the - tapered shield s ction 216 and the di~tal shield section 218 of ths needle shield assembly 210 extend beyond the distal ne~dle point 179 of the ne~dle assembly 176 and the 20 end rim 2~2 on the p:roximal end of ~he proYi ~1 ~hield section 214 contacts the proximal end of the collar - 'ly 186. In this extended position, the proxiDlal end of the keys 198 ar~ positioned adjacent to th~ proximal :~ side o~ the keyways 190 and the flat-proximal ~nds of the ' 25 }ceys 198 are located along the di~tal edge o~ the spherical detents 208 and adjacent to the walls, 202 and 204 and lo~ slots 206.
.. '. I~ the user desires to lock the n~dle shield assembly 210 in a locked and extended position (Figure 3 ) rather than the releasable extended position described above, the user may rotate the needle shield asse~bly 210 cloc~wise or counterclockwise about the cartridge holder assembly 166 and tbe collar as~embly 186. Rotation of the needle shield .' asse~bly 210 will cause the keys l~B on the needle shield ., 35 ~ hly 210 to move over the ramp shaped ~ur~ace of the $ ~

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WO 92/l~lX3 PC'~I'/IJS()I/02S7() 2 0 ~ ~ 3 7 :1 adjacent walls, 202 or 204, on the collar assembly 1~6 until the keys 198 ~all into the locking slots 206 ïormed therebetween. When the keys 198 are positioned in the locking slots 206, the flat~p:roximal end of each key 198 5 abuts against the distal ~ur~ace 196 o~ one of the protrusions 188 so that the shield cannot b2 moved pro~ -1 ly and returned to thlg retrac~ed position. E~ecause .~ of the interlocking relationehip b2tween the sides of the keys 198 and the perpendicular side surfac:es o~ the walls, 10 202 and 204, the needl~ shield ;~8~hly 210 ::an no longer be rctated and, accordingly, the needle ~hield as~;embly 210 is in a lock~d and ~xtended E~osition (Figure ~).
In c~3rtain sit:uat~ons, it ~nay ~3e de ~rabl~ to ~ove the ne~dle shield as~embly 210 to the ext~nde~7 position (Fi~ure 15 5) without having the needle shield assembly 210 in a '~ locked and exten~le~ position (Figure ~)0 For example, if a ~- dental syxinge 150 i~; preloaded with the medication cartridçre 1~7 at a location remote ~ro~ the patierlt; stored on a denkal tray prior to use or if th~ user desir~s to 20 verify that the sledication cartridge 167 i-~: properly seated in the cartridge hn~ d~r ~ mhly 16S ~ ~ay be prefer~ble to extend the l~eedle shield a~3embly 210 beyond the distal '~ needle point 179 so that the rleedle shield ass~mbly 210 f~nctions as a t'-,~oL~ry pro~ective element prior to the .; 25 actual u~e of the d~ntal syringe lS0. Use o~ the dental syringe 150 in this manner i5 ~acilitated by the spherical .'. det~nts 208 on the collar assembly 186. As described ; above, these spherical detents 208 are located in each of . the keyways 190 between the protrusions 188 so that when the n~edle shield assembly 210 is pushed to th~ extended position, the ~lat-proximal end o~ each of the keys 198 will relea5e from the spherical det~nts 208 and the end rim :'~ 222 of the ~eedle shield assembly 210 will contact the proximal end o~ the collar 186. The spheric~l detents 208 - 35 prevent the n~edle shield assembly 210 ~rom being ,.
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:'1 , , WO 9~/lX1~3 PCr/lJS')1/02S79 ~,~

accidentally or inadvertenkly re!tracted unles~ su~ficient proximal ~orce is applied to the needle ~hi~ld ~ mhly 210 to ~ove the keys 198 pr~Y; -lly over the ~ph~rical detents ~08. Onc~ the injection has been ~r;ni~tered~ the ~eedl~
shi~ld A~8f hly 210 ~ay be ~ov~d di tat ly to ~he ext~n~
:~ position and then rotated ~o ~hat the key~ 198 ~all into the locking slots 206 to lock the needl~ shi~ld as~embly : 210 in the locked and extended position a~ described abov2.
I~ this liqht, it ~hould ~e appr~ciat~d that the present invention provides a ~afety dental syringe which :i allows a ~edication cartridge to be in~rted into the dental syrin~e through the pr~ 1 end ~h~r~o~.
~ Additionally, the rD~l~.c~ dia~eter di~tal end ~f the .~ pre~ent invention allows the u~er to observ~ th~ dist21 end o~ the needle during a dental procedure ~nd does not interfere ~ith any oth~r instru~ents whicb may b~ present in ~he patient' 6 ~outh. The relatively ~all ~ize of the :.
~ needle ap~rture in the di~tal end of t~e needl~ ~hield also :~ preven~s accidental contact wi~h ~h~ distal needle point ~;- 20 when ~he needle shield i~ in ~he extended position.
Finally, the cylindrical sh~pe o~ the distal end of the needle shield allows the user to ~ove the needle shield to the ext~ po~ition to verify that the ~edicatlon .~ cartridge is properly seated in the cartridge holder without removing the needle sheath.
It should be furth~r understood that the above described e~bodiments may be modified in certain aspects ~. for use on nearly any medical, or laboratory syringe.
;, Additionally, it i5 anticipated that the present invention may be used with a pre~illed ~yringe wherein the use of a separate medication be~ween a proximal plunger member and th~ distal barrel section. There~ore, the foregoing is ,~- inten~e~ to be descriptive of the preferred form of the embodiments described above while the saope of the pre~ent .. . .
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WO 92/lXlX3 PCr/l,S91/02579 19 ~ ~ ~ 3 7 1 , ' inventiorl is intended to ~e defi.ned by th~ ~ollowing clai=s.

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Claims

1. A medication containing syringe comprising:
a first tubular member having distal and proximal ends and adapted to receive a medication cartridge therein;
a plunger rod assembly including a reciprocally mounted plunger rod mounted adjacent said proximal end of said first tubular member and adapted to contact a portion of the medication cartridge;
a double ended hollow needle assembly including a needle hub thereon, said needle hub being operatively mounted on said distal end of said first tubular member, said needle assembly having a needle point on the distal and proximal ends thereof whereby said proximal needle point of said needle assembly is adapted to pierce the medication cartridge for fluid communication with the medication contained therein and said distal needle point of said needle assembly extends distally beyond said distal end of said first tubular member;
collar means operatively associated with said first tubular member, said collar means including recessed keyway thereon;
a second tubular member positioned about said first tubular member and said collar means, said second tubular member having distal and proximal ends and an inwardly directed and elongate key thereon and wherein the length of said key is greater than the length of said keyway and said key slidably contacts said collar means, said second tubular member being longitudinally movable over said first tubular member and said collar means between a retracted position wherein said distal needle point is exposed and an extended position wherein said distal needle point is protected; and a funnel shaped member on the distal end of said second tubular member and said funnel shaped member including an attachment means on the distal end of the funnel shaped member wherein said attachment means has an outer diameter which is substantially smaller than the outer diameter of said proximal end of said second tubular member such that said attachment means is adapted to retain a needle sheath thereon.

2. The medication containing syringe of claim 1, wherein locking means are provided between said second tubular member and said collar means and said second tubular member is rotatably movable from said extended position to a locked and extended position wherein said second tubular member is prevented from being returned to said retracted position.

3. The medication containing syringe of claim 2, wherein said second tubular member includes said key thereon to facilitate the coaxial movement of said second tubular member along said collar means and said first tubular member between said retracted and extended positions.

4. The medication containing syringe of claim 3, wherein said locking means includes a plurality of walled recesses about the periphery of said collar means to lock a portion of said key between said walls when said second tubular member is moved from said extended position to said locked and extended position.

5. The medication containing syringe of claim 1, wherein said distal end of said second tubular member is adjacent said needle hub when said second tubular member is in said retracted position and said distal end of said second tubular member extends distally of said distal needle point when said second tubular member is in said extended position.

6. The medication containing syringe of claim 1, wherein said plunger rod assembly further includes an injector assembly operatively connected to the proximal end of said first tubular member, said injector assembly including a longitudinally extending bore slidably receiving said plunger rod therein, the distal end of said plunger rod having a connecting means mounted thereon, said connector means being adapted to connect said plunger rod to a plunger means mounted in the proximal end of the medication cartridge for delivery of the medication from the medication cartridge through said hollow needle assembly upon longitudinal movement of said plunger rod toward said distal end of said first tubular member.

7. A prefilled syringe comprising:
a barrel member having distal and proximal ends and said barrel member adapted to receive a medication cartridge therein;
an elongate and hollow needle operatively mounted on said distal end of said barrel member, a first portion of said needle extends distally beyond said distal end of said barrel member to a distal needle point and a second portion of said needle extends proximally from and within said distal end of said barrel member to a proximal needle point;
a cylindrical medication cartridge positioned within said barrel member and having distal and proximal ends, said distal end including a needle pierceable diaphragm thereon and said proximal end including a movable plunger means mounted therein;
an injector assembly positioned adjacent said proximal end of said barrel member and including a plunger rod assembly reciprocally mounted thereon, said plunger rod assembly including a distal end having a connector means thereon adapted to connect said plunger rod assembly to said plunger means in said medication cartridge;
a collar operatively connected to said barrel member, said collar means including at least one pair of protrusions extending radially therefrom to form a keyway therebetween said keyway including distal and proximal ends thereon;
an elongate needle shield means having distal and proximal ends wherein said shield means is movable over said collar means between a retracted position wherein said distal needle point is exposed and an extended position wherein said distal needle point is protected, an interior surface on said shield means including at least one longitudinally extending key thereon, said key having distal and proximal ends thereon and the distance between the distal and proximal ends of said keyway is less than the distance between said distal and proximal ends of said key and said key being adapted to be movable in said keyway between said protrusions on said collar means as said shield means is moved between said retracted position and said extended position; and a funnel shaped member on the distal end of said shield means and including a distal attachment means thereon and said attachment means having an outer diameter substantially smaller than the outer diameter of said proximal end of said shield means such that said attachment means is adapted to retain a needle sheath thereon.

8. The prefilled syringe of claim 7 further including a locking member having at least one recess therein on said collar means and said key on said shield means being adapted to be rotatable into said locking member recess when said shield means is in said extended position to rotate said shield to a locked and extended position wherein said shield means is prevented from returning to said retracted position by said locking member on said collar means.

9. The prefilled syringe of claim 8, wherein said locking member recess is formed by a pair of radially extending parallel wall members having a ramp shaped side surface on at least one of said wall members and wherein said key on said shield means is rotatable over said side surface and into said locking member recess when said shield means is in said extended position.

10. The prefilled syringe of claim 7 further including at least one detent on said distal end of said shield means to contact one of said protrusions on said collar means to releasably retain said shield means in said retracted position.

11. The prefilled syringe of claim 7 further including an inwardly extending rim member on said proximal end of said shield means, said rim member being adapted to abut against said collar means to limit the distal movement of said shield means along said barrel member.

12. A prefilled syringe, comprising:
an elongate and tubular barrel member having distal and proximal ends thereon and adapted to receive a medication cartridge therein;
a plunger rod assembly including a reciprocally mounted plunger rod mounted adjacent said proximal end of said barrel member and adapted to contact a portion of the medication cartridge;
an elongate and hollow needle assembly having a point on the distal end thereof and said needle assembly being operatively mounted on said distal end of said barrel member;
collar means operatively connected to said barrel member, said collar means including a longitudinally oriented keyway thereon;
a shield means having cylindrically shaped distal and proximal ends and a tapered section between said distal and proximal ends thereof and an inwardly directed and longitudinally oriented key on the inner surface thereof, said key being longer than said keyway on said collar means and wherein the outer diameter of said distal end of said shield means is smaller than the outer diameter of said proximal end of said shield means;
a hollow needle sheath means closed at the distal end thereof removably mounted on said distal end of said shield means; and said shield means being longitudinally slidable relative to said collar means, said shield means being movable between a retracted position wherein said distal needle point is exposed and an extended position wherein said distal needle point is protected.

13. The syringe of claim 12 further including at least one locking member having a recess therein on the distal end of said collar means, at least one key on said shield means wherein said locking member is adapted to lock at least a portion of said key therein when said shield means is rotated from said extended position to a locked and extended position wherein said key is in said recess and said shield means is prevented from being returned to said extended position.

14. The syringe of claim 12 further including at least one pair of protrusions extending radially from said collar means and a key extending lengthwise along the interior surface of said shield means and said protrusions having a radially extending detent therebetween wherein said detent is adapted to contact said key on said shield means to releasably retain said shield means in said extended position.

15. A prefilled syringe comprising:
an elongate first tubular member having distal and proximal ends;
a hollow double ended needle assembly operatively mounted on said distal end of said first tubular member, said needle having needle points on the distal and proximal ends thereof;
a cylindrical medication cartridge adapted to contain medication therein and being received in said first tubular member, said medication cartridge including a proximal end having a movable plunger means therein and a distal end including a cap member having an orifice therein mounted thereon, said cap member including a needle pierceable diaphragm therein adjacent said orifice and said diaphragm being adapted to be pierced by said proximal needle point;
an injector assembly positioned adjacent the proximal end of said first tubular member, said injector assembly including an elongate and reciprocally movable plunger rod slidably received in a longitudinally extending bore in said injector assembly, said plunger rod assembly including a connecting means on the distal end thereof adapted to connect said plunger rod assembly to said plunger means of said medication cartridge;
a collar means having distal and proximal ends, said collar means operatively connected to said first tubular member and including a plurality of spaced apart protrusions forming a keyway therebetween and a plurality of locking members extending radially therefrom said locking members having recesses therein and being positioned adjacent to the distal surface of said protrusions on said collar means; and an elongate and tubular shield means having distal and proximal ends and at least one elongate key extending longitudinally along the internal surface of said shield means, said key having distal and proximal ends thereon and being adapted to move longitudinally through said keyway on said collar as said shield means is moved between a retracted position wherein said distal needle point is exposed and an extended position wherein said distal needle point is protected by said shield means, and the length of said key is greater than the length of said keyway on said collar means and wherein said key is rotatable into said recesses of said locking members on said collar means when said shield means is in said extended position to move said shield means to a locked and extended position wherein said shield means is prevented from being returned to said retractable position.

16. A prefilled syringe of claim 15 further including a radially extending detent positioned between said protrusion wherein said detent is adapted to contact at least a portion of said key as said shield means is moved between said retracted position and said extended position.

17. The prefilled syringe of claim 15, wherein said locking members are formed by pairs of wall members and at least one of each pair of said wall members which includes a ramp shaped side surface thereon, said wall members being positioned distally of said protrusions on said collar means such that said key is rotatable over said ramp -shaped side surface and into said recess in one of said locking members.

18. A prefilled syringe comprising:
an elongate first tubular member including distal and proximal ends;
a double ended hollow needle assembly operatively mounted on said distal end of said first tubular member, said needle assembly including a needle point on the distal and proximal ends thereof;
a cylindrical medication cartridge having a medication therein and adapted to be received in said first tubular member, said medication cartridge including distal and proximal ends, said proximal end including a movable plunger means therein and said distal end including a cap means thereon, said cap means including an orifice therein and a needle pierceable diaphragm thereon, said diaphragm being adapted to be pierced by said proximal needle point;
an injector assembly operatively connected to the proximal end of said first tubular member, said injector assembly including an elongate plunger rod assembly slidably received in an elongate bore extending through said injector assembly, said plunger rod assembly having a distal end adapted to engage said plunger means in said proximal end of said medication cartridge;
collar means operatively connected to the distal end of said first tubular member and including an external surface having a plurality of spaced apart pairs of protrusions and at least one locking member thereon wherein said locking member includes at least one recess therein and being positioned distally of said protrusions on said collar means, said locking members further including a pair of radially extending wall members wherein at least one of said wall members includes a ramp shaped side surface thereon and wherein said pairs of protrusions form keyways therebetween;
an elongate and tubular shield means having distal and proximal ends and a plurality of elongate keys extending longitudinally along the interior surface of said shield means between said distal and proximal ends thereof wherein said keys are longer than said keyways on said collar means and are adapted to move longitudinally in said keyways between said protrusions as said shield means is moved between a retracted position wherein said distal needle point is exposed and an extended position wherein said distal needle point is protected and wherein said keys are rotationally movable over said side surface of said wall members and into said locking member to move said shield means from said extended position to a locked and extended position wherein said shield means is prevented from being returned to said retracted position;
said distal end of said shield means including a cylindrical distal portion having an outer diameter smaller than the outer diameter of said proximal end of said shield means; and a tubular needle sheath means having a closed distal end thereon said needle sheath being removably mounted about said distal portion of said shield means to protect said distal needle point.

19. A medication containing syringe comprising:
a first tubular member having distal and proximal ends and a slidable member adapted to retain a prefilled quantity of medication distally thereof;
a plunger rod assembly including a plunger rod adapted to contact said slidable member through said proximal end of said first tubular member;
a double ended hollow needle assembly including distal and proximal ends and a needle hub thereon, wherein said needle hub is operatively mounted on said distal end of said first tubular member, said needle assembly includes a distal needle point on said distal end thereof and said proximal end of said needle assembly is adapted to be in fluid communication with the medication retained distally of said slidable member and said distal needle point of said needle assembly extends distally beyond said distal end of said first tubular member;

collar means operatively connected to said first tubular member said collar means including a keyway thereon oriented longitudinally with respect to said first tubular member;
a second tubular member positioned about said first tubular member and said collar means, said second tubular member having distal and proximal ends and a key extending inwardly and longitudinally therealong, said key having distal and proximal ends and the length of said key is greater than the length of said keyway on said collar means such that said second tubular member is longitudinally movable over said first tubular member and said collar means between a retracted position wherein said distal needle point is exposed and an extended position wherein said distal needle point is protected; and said second tubular member further including a tapered section on the distal end thereof and the outer diameter of said distal end of said tapered section is smaller than the outer diameter of said proximal end of said second tubular member and when said second tubular member is in said retracted position, said distal end of said second tubular member is adjacent to said needle hub and said distal end of said first tubular member.

20. The medication containing syringe of claim 19, wherein locking means are provided between said second tubular member and said collar means and said second tubular member is rotatably movable from said extended position to a locked and extended position wherein said second tubular member is prevented from being returned to said retracted position.

21. The medication containing syringe of claim 19, wherein said key and said keyway facilitate longitudinal and linear sliding movement of said second tubular member along said collar means and said first tubular member between said retracted and said extended positions.

22. The medication containing syringe of claim 21, wherein said key is provided on an interior surface of said second tubular member and a locking means is radially spaced apart from said keyway on said collar means and includes a plurality of walled recesses about the periphery of said collar means to lock a portion of said key between said walls when said second tubular member is moved from said extended position to said locked and extended position.

23. The medication containing syringe of claim 19, wherein said tapered section on said distal end of said second tubular member includes a funnel-shaped portion having an attachment means on the distal end thereof and wherein a hollow needle sheath is removably mounted about said attachment means to protect said distal needle point when said second tubular member is in said retracted position.

24. The medication containing syringe of claim 19, wherein said distal end of said second tubular member is adjacent said needle hub when said second tubular member is in said retracted position and said distal end of said second tubular member extends distally of said distal needle point when said second tubular member is in said extended position.

25. The medication containing syringe of claim 19, wherein said plunger rod engages said slidable member to enable said slidable member to be moved in said first tubular member in response to longitudinal movement of said plunger rod in said first tubular member.

26. A prefilled syringe comprising:
an elongate first tubular member having distal and proximal ends;
a slidable member slidably operatively mounted in said first tubular member and adapted to retain a prefilled medication distally thereof;
an injector assembly operatively associated with said first tubular member and including a reciprocally mounted plunger rod adapted to extend into said proximal end of said first tubular member and engage said slidable member to enable movement thereof;
a double ended hollow needle assembly having distal and proximal ends, wherein said needle assembly is operatively mounted on said distal end of said first tubular member and said distal end of said needle assembly includes a distal needle point thereon and said proximal end of said needle assembly is adapted to be in fluid communication with the prefilled medication contained in said first tubular member;
collar means including distal and proximal ends with a keyway extending therebetween and said collar means is operatively associated with said first tubular member;
an elongate second tubular member coaxially positioned about first tubular member and said collar means, said second tubular member having distal and proximal ends and including an inwardly directed key thereon, said key including distal and proximal ends such that the distance between said distal and proximal ends of said key is greater than the distance between said distal and proximal ends of said collar means and said keyway and said second tubular member is longitudinally movable over said first tubular member and collar means between a retracted position wherein said distal needle point is exposed and an extended position wherein said distal needle point is protected; and said second tubular member further including a tapered section on the distal end thereof and the outer diameter of said distal end of said tapered section is smaller than the outer diameter of said proximal end of said second tubular member and when said second tubular member is in said retracted position, said distal end of said second tubular member is adjacent to said needle hub and said distal end of said first tubular member.

27. The prefilled syringe of claim 26 wherein said second tubular member slidably contacts said collar means and locking means are provided between said second tubular member and said collar means.

28. The prefilled syringe of claim 27 wherein said second tubular member is slidable in said keyway on said collar means and is rotatable about said first tubular member in said extended position between a releasable extended position and a locked and extended position.

29. A syringe assembly adapted to receive a prefilled container of medication therein, said syringe assembly comprising:
an elongate and tubular barrel member having distal and proximal ends thereon and adapted to receive a medication containing cartridge therein;
a plunger rod assembly including a reciprocally mounted plunger rod mounted adjacent said proximal end of said barrel member and adapted to contact a portion of the medication containing cartridge;
a needle assembly having distal and proximal ends with a needle point on said distal end, said needle assembly being mounted in fluid communication with said distal end of said barrel member;
collar means operatively associated with said barrel member, said collar means including a keyway thereon, said keyway being longitudinally oriented with respect to said barrel member;
elongate and generally cylindrical shield means coaxially oriented with respect to said barrel member and said collar means, said shield means including distal and proximal ends and a tapered section therebetween such that the diameter of said distal end of said shield means is less than the diameter of said proximal end of said shield means, said shield means further including an inner surface having an elongate key thereon, said key including distal and proximal ends thereon and the length of said key is greater than the length of said keyway on said collar means and said shield means is longitudinally slidable relative to said collar means between a retracted position wherein said needle point on said distal end of said needle is exposed and an extended position wherein said needle point is protected.

30. The syringe of claim 29 wherein said tapered section of said shield means is adjacent said distal end of said shield means such that said tapered section is adjacent said collar means when said shield means is in said retracted position and spaced apart therefrom when said shield means is in said extended position.

31. The syringe of claim 29 further including a hollow needle sheath means, said sheath means including a closed distal end and an open proximal end, said proximal end of said sheath means being sized to be removably mounted on said distal end of said shield means.